Thank you for a great response very detailed more than I expected. Will try this when we come off the road nest month.There are several things that can be done to help. Part of the problem is that the vibrations from the pump are transmitted by the PEX water lines through the RV to act much like the sound box of a guitar. What I have done is to mount the pump to rubber floor mat material and then put a second layer of mat under the screw heads holding the pump, and fasten the two layers of mat to the floor. I don't have pictures any more but doing that eliminates any solid mount between the pump and the floor. Amazon now sells a kit to do essentially the same as what I did.
You can also eliminate the transmission of the pump vibrations to the Pex plumbing with flex couplings such as these from Amazon.